Ultimately, two animals with very similar anatomies can move differently, and two with different anatomies can move in the same way. This means that Danuvius may not be able to serve as a model for our ancestors’ behavior, even if its anatomy is similar to theirs.

In fact, we believe there are other plausible interpretations of Danuvius’s bones. These alternatives give a picture of a repertoire of potential movements that may have been used in different contexts.

For example, one of Danuvius‘s most striking features is the high ridge on the top of its shinbone, which the researchers say is associated with “strongly developed cruciate ligaments,” which stabilize the knee joint. The researchers link these strong stabilizing ligaments with evidence for an extended hip and a foot that could be placed flat on the floor to suggest that this ape habitually stood upright. Standing upright could be a precursor to bipedal walking, so the authors suggest that this means Danuvius could have been like our last shared ancestor with other apes.

However, the cruciate ligaments also work to stabilize the knee when the leg is rotating. This only happens when the knee is bent with the foot on the ground. This is why skiers who use knee rotation to turn their bodies often injure these ligaments.

Other explanations

We have not seen the Danuvius bones in real life. But, based on the researchers’ excellent images and descriptions, an equally plausible interpretation of the pronounced ridge on the top of the shinbone could be that the animal used its knee when it was bent, with significant rotational movement.

Perhaps it hung from a branch above and used its feet to steer by gripping branches below, rather than bearing weight through the feet. This could have allowed it to capitalize on its small body weight to access fruit on fine branches. Alternatively, it could have hung from its feet, using the legs to maneuver and the hands to grasp.

All of these movements fit equally well with Danuvius’ bones, and could be part of its movement repertoire. So there is no way to say which movement is dominant or typical. As such, any links to our own bipedalism look much less clear-cut.

Danuvius is undoubtedly a very important fossil, with lots to teach us about how varied ape locomotion can be. But we would argue that it is not necessarily particularly like us. Instead, just like living apes, Danuvius would probably have displayed a repertoire of different movements. And we can’t say which would have been typical, because anatomy is not enough to reconstruct behavior in full.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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